Split landing hero into interactive webcam grid

- Move hero into its own client component
- Add webcam-backed pixel grid background
- Update landing wiring and content test coverage

tests/landing-content.test.mjs

@@ -2,10 +2,15 @@ import { readFile } from "node:fs/promises";
 import test from "node:test";
 import assert from "node:assert/strict";
 
-const componentPath = new URL("../src/components/landing.tsx", import.meta.url);
+const sourcePaths = [
+  new URL("../src/components/landing.tsx", import.meta.url),
+  new URL("../src/components/landing-hero-section.tsx", import.meta.url),
+];
 
 test("Landing component contains the core brief anchors", async () => {
-  const source = await readFile(componentPath, "utf8");
+  const source = (
+    await Promise.all(sourcePaths.map((p) => readFile(p, "utf8")))
+  ).join("\n");
 
   for (const phrase of ["Projektbrief", "01", "Website", "Kontakt", "für", "müssen", "Änderungen"]) {
     assert.match(source, new RegExp(phrase));
@@ -13,7 +18,9 @@ test("Landing component contains the core brief anchors", async () => {
 });
 
 test("Landing component uses real German umlauts in visible copy", async () => {
-  const source = await readFile(componentPath, "utf8");
+  const source = (
+    await Promise.all(sourcePaths.map((p) => readFile(p, "utf8")))
+  ).join("\n");
 
   for (const asciiFallback of [
     "fuer",